Bionic shale inhibitor and preparation method thereof and drilling fluid

Abstract

The present invention discloses a bionic shale inhibitor, consisting of structural units denoted by formula (1) and structural units denoted by formula (2), wherein, the molar ratio of the structural units denoted by formula (1) to the structural units denoted by formula (2) is 0.2-6:1, and the weight-average molecular weight of the shale inhibitor is 800-4,000 g / mol. The present invention further provides a method for preparation of a bionic shale inhibitor. The present invention further provides a drilling fluid containing the bionic shale inhibitor. The bionic shale inhibitor disclosed in the present invention has high shale inhibition capability, and is environment-friendly and pollution-free.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to Chinese Patent Application No. 201510064987.8 filed on Feb. 6, 2015 and entitled “BIONIC SHALE INHIBITOR AND PREPARATION METHOD THEREOF, AND DRILLING FLUID AND USE THEREOF”, the entire content of which is fully incorporated here by reference.FIELD OF THE INVENTION[0002]The present subject matter relates to a bionic shale inhibitor, a method for preparation of the shale inhibitor and a drilling fluid.BACKGROUND OF THE INVENTION[0003]Maintaining the stability of well walls of bored walls is a world-wide problem in the well drilling industry, and that problem exists in many oil fields in the world, and has not been solved well up to now. As the target of oil and gas exploration and development in China is further turned to unconventional resources such as deep-seated oil and gas resources, coal-seam gas reservoirs, and shale gas reservoirs under complex geological conditions, the well wall stability proble...

AI Technical Summary

Benefits of technology

The patent text describes a new type of polyamino acid that can be used as a bionic shale inhibitor in drilling fluids. This inhibitor helps to prevent instability in the shale well walls. It is easy to break down and environmentally friendly. The inhibitor contains a high number of positive charges that can enter the pores in clay shale and attach to the surfaces of clay minerals. This prevents the swelling pressure caused by clay and maintains the stability of the well wall.

Problems solved by technology

Maintaining the stability of well walls of bored walls is a world-wide problem in the well drilling industry, and that problem exists in many oil fields in the world, and has not been solved well up to now.

As the target of oil and gas exploration and development in China is further turned to unconventional resources such as deep-seated oil and gas resources, coal-seam gas reservoirs, and shale gas reservoirs under complex geological conditions, the well wall stability problem is often encountered in the exploration and drilling process, resulting in lower drilling speed in complex deep wells and horizontal shale gas wells, increased accidents, longer drilling cycle, and higher cost.

That problem has severely affected the exploration and development process in important oil and gas resource replacement regions in China.

Especially, in the oil and gas fields in the western regions in China (e.g., in Sichuan and Chongqing area), the geological conditions are extremely complex, and complex accidents, such as well wall collapse, well leakage, diameter shrinkage, jamming of drilling tools, logging blocking, and low cementing quality, etc., may occur easily at locations where the formation is high and steep, the strata are fractured, or the well traverses clay shale sections at a great deviation angle or horizontally.

Consequently, not only the drilling cycle may be delayed, but also severe economic loss may occur.

90% borehole wall instability accidents in the well drilling process happen in the clay shale formation, where the dispersion and flaking-off of clay shale resulted from hydrated swelling of clay in the clay shale is the root cause for well wall instability.

However, as the national environmental laws become strict increasingly, the application of oil-based drilling fluids is restricted owing to the severe damages of oil-based drilling fluids to the environment.

Since neutralizing the negative charges on the clay surface is the main approach for inhibiting hydrated dispersion, the shale inhibitors in almost all water-based drilling fluids commonly used in China and foreign countries presently are mainly cationic polymers, including cationic polyacrylamides, polyamines (e.g., poly-dimethyl diallyl ammonium chloride), and polyether amines (e.g., polyether diamine), etc.. However, most cationic polymer inhibitors are usually non-biodegradable and have more or less damages to the environment, except polyether amine inhibitors.

Therefore, they have very limited inhibition capability against hydrated swelling of clay.

Images